1. Field of the Invention
This invention relates to a device for transmitting a thrust from one of a pair of adjacent pipes so as to propel the other in a pipe propelling method.
2. Description of the Prior Art
As for one of methods for constructing a pipeline in the ground, there has been proposed a pipe propelling method, in which a plurality of pipes are sequentially forced into the ground in series. According to this pipe propelling method, end faces of adjacent pipes face to each other through a flange provided on a tubular collar for receiving pipe ends. Also, a thrust to be applied to a leading pipe is transmitted from the following pipes through the flange.
In the conventional pipe propelling method, when the adjacent pipes pass through a straight portion of the pipeline to be constructed, the whole end faces of the adjacent pipes are in contact with the flange, so that the thrust acts uniformly on the whole end faces of the adjacent pipes. However, when the leading pipe differs from the following pipe in the propelling direction in such a case that the adjacent pipes pass through a curved portion of the pipeline to be constructed, the leading pipe is inclined to the following pipe, so that the thrust is transmitted through part of the adjacent pipes. Consequently, according to the conventional pipe propelling method, the thrust is concentrated on a portion of the pipe, thus resulting in the occurrence of cracks on the pipe portion and breakage of the pipe portion.
To prevent these problems, there has been proposed the following prior art method, in which a connecting mechanism provided with a plurality of jacks is disposed between adjacent pipes, and a predetermined jack is operated to incline the leading pipe to the following pipe when these adjacent pipes pass through a curved portion of a pipeline to be constructed. In this prior art method, however, since the connecting mechanism has to be finally removed, this method can not be used when constructing a the pipeline having such a small bore that an operator cannot enter to remove the connecting mechanism.